Most boiler component structures are mainly fabricated by welding which are likely to be regions of crack initiation and propagation. However, the technique of predicting the life of creep crack initiation and growth have not been clearly developed for weldments of W-added 9%Cr ferritic heat-resistant material (ASME Code Case 2179, ASTM A335 P92) due to many factors such as the variation in micro-structure and the residual stresses caused by welding and thermal cycles. In the present paper, high temperature creep crack growth tests were conducted using C(T) specimens with the cracks in the heat affected zone of weldments for P92. To derive the algorithm of predicting the life of creep crack growth, the creep crack growth rate were estimated by C*, dδ/dt and Q* parameters. Additionally, the definition and estimation method of creep crack initiation and growth life for weldments were discussed on the basis of the concept of structural brittleness.
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